U.S. Pat. No. 4,742,593 to Kallenbach illustrates, in its FIGS. 4 and 6, exemplary valves for use in water-interruption-type automatic swimming pool cleaners. The depicted valves, which generally are tubular in shape, form parts of the principal fluid flow paths from entrances into the cleaners to exits upstream thereof. As indicated in the Kallenbach patent, whose contents are incorporated herein in their entirety by this reference, the valves expand and contract autonomously when upstream suction is applied.
Because the valves flex in use, they typically are made of elastomeric material. Polyurethane, for example, is a soft plastic from which the valves may be formed. Regardless of the material used to form the valves, its hardness typically would comprise a value on the Shore A durometer scale.
Also as noted in the Kallenbach patent, the outlet end of each valve is designed to connect to an inlet end of an elongated, rigid tubular section or pipe. The rigid pipe continues the principal fluid flow path through the cleaner upstream of the valve. Because it is not needed to flex in use, the rigid pipe typically is made from a plastic material much harder than the plastic of the valve so as to maintain its structural integrity when subjected to suction. Consequently, the hardness of the pipe is usually a value selected from the Shore D durometer scale or harder.
Although necessary for proper functioning of the cleaners of the Kallenbach patent, the connection of a soft, flexing valve to a hard, rigid pipe is not without difficulties. In particular, as the valve moves relative to the rigid pipe, repeated contact between the two components causes the softer valve material to wear. This wear reduces overall durability of the valve and, if possible, should be avoided.